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There is an increased interest in the use of cellulose nanocrystal (CNC) films and coatings for a range of functional applications in the fields of material science, biomedical engineering, and pharmaceutical sciences. Most of these applications have been demonstrated on films and coatings produced using laboratory-scale batch processes, such as solvent casting, dip coating, or spin coating. For successful coating application of CNC suspensions using a high throughput process, several challenges need to be addressed: relatively high viscosity at low solids content, coating brittleness, and potentially poor adhesion to the substrate. This work aims to address these problems. The impact of plasticizer on suspension rheology, coating adhesion, and barrier properties was quantified, and the effect of different pre-coatings on the wettability and adhesion of CNC coatings to paperboard substrates was explored. CNC suspensions were coated onto pre-coated paperboard in a roll-to-roll process using a custom-built slot die. The addition of sorbitol reduced the brittleness of the CNC coatings, and a thin cationic starch pre-coating improved their adhesion to the paperboard. The final coat weight, dry coating thickness, and coating line speed were varied between 1–11 g/m 2 , 900 nm–7 µm, and 2.5–10 m/min, respectively. The barrier properties, adhesive strength, coating coverage, and smoothness of the CNC coatings were characterized. SEM images show full coating coverage at coat weights as low as 1.5 g/m 2 . With sorbitol as plasticizer and at coat weights above 3.5 g/m 2 , heptane vapor and water vapor transmission rates were reduced by as much as 99% and 75% respectively. Compared to other film casting techniques, the process employed in this work deposits a relatively thick coating in significantly less time, and may therefore pave the way toward various functional applications based on CNCs. Graphical abstract

Glucose oxidase (EC 1.1.3.4) sensors that have been developed and widely used for glucose monitoring have generally relied on electrochemical principle. In this study, the potential use of colorimetric method for glucose detection utilizing glucose oxidase-magnetic cellulose nanocrystals (CNCs) is explored. Magnetic cellulose nanocrystals (magnetic CNCs) were fabricated using iron oxide nanoparticles (IONPs) and cellulose nanocrystals (CNCs) via electrostatic self-assembly technique. Glucose oxidase was successfully immobilized on magnetic CNCs using carbodiimide-coupling reaction. About 33% of GOx was successfully attached on magnetic CNCs, and the affinity of GOx-magnetic CNCs to glucose molecules was slightly higher than free enzymes. Furthermore, immobilization does not affect the specificity of GOx-magnetic CNCs towards glucose and can detect glucose from 0.25 mM to 2.5 mM. Apart from that, GOx-magnetic CNCs stored at 4 °C for 4 weeks retained 70% of its initial activity and can be recycled for at least ten consecutive cycles.

Poly (vinyl pyrrolidone) (PVP)/cellulose nanocrystal (CNC)/silver nanoparticle composite fibers were prepared via electrospinning using N,N′-dimethylformamide (DMF) as a solvent. Rheology, morphology, thermal properties, mechanical properties, and antimicrobial activity of nanocomposites were characterized as a function of material composition. The PVP/CNC/Ag electrospun suspensions exhibited higher conductivity and better rheological properties compared with those of the pure PVP solution. The average diameter of the PVP electrospun fibers decreased with the increase in the amount of CNCs and Ag nanoparticles. Thermal stability of electrospun composite fibers was decreased with the addition of CNCs. The CNCs help increase the composite tensile strength, while the elongation at break decreased. The composite fibers included Ag nanoparticles showed improved antimicrobial activity against both the Gram-negative bacterium Escherichia coli (E. coli) and the Gram-positive bacterium Staphylococcus aureus (S. aureus). The enhanced strength and antimicrobial performances of PVP/CNC/Ag electrospun composite fibers make the mat material an attractive candidate for application in the biomedical field.

Carboxylated cellulose nanocrystals (CCN) and cellulose nanocrystals (CNC) were prepared from borer powder of bamboo by two different kinds of procedures: one-step approach with ammonium persulfate for CCN and two-step approach with sulfuric acid for CNC. The obtained samples were characterizated by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results show that the particles of CCN and CNC present spherical shape with diameters of 20–50 and 20–70 nm, respectively. The crystallinity of CCN and CNC is significantly improved after a series of chemical treatment, which is up to 62.75 and 69.84 %, respectively. The research indicates that the borer powder from bamboo could be an excellent raw material for manufacturing CNC in a low-cost and environmental-friendly way. Rational and sustainable utilization of the bamboo borer powder to develop new bioproducts holds great potential value for industry and offers many benefits and opportunities.

A fibrillar hydrogel was obtained by covalent crosslinking via Diels–Alder reaction of two types of cellulose nanocrystals (CNCs) with furan and maleimide groups. Gelation has been studied at various ratios of components and temperatures in the range from 20 to 60 °C. It was shown that the rheological properties of the hydrogel can be optimized by varying the concentration and ratio of components. Due to the rigid structure of the CNCs, the hydrogel could be formed at a concentration of at least 5 wt%; however, it almost does not swell either in water with pH 5 or 7 or in the HBSS buffer. The introduction of aldehyde groups into the CNCs allows for the conjugation of physiologically active molecules containing primary amino groups due to the formation of imine bonds. Here, we used benzocaine as a model drug for conjugation with CNC hydrogel. The resulting drug-conjugated hydrogel demonstrated the stability of formulation at pH 7 and a pH-sensitive release of benzocaine due to the accelerated hydrolytic cleavage of the imine bond at pH < 7. The developed drug-conjugated hydrogel is promising as wound dressings for local anesthesia.

In a world increasingly focused on environmental sustainability and the imperative of efficient waste management, innovative approaches in material science are becoming crucial. This research is centered on the synthesis of cellulose nanocrystals (CNCs) from post-use exam waste paper and the development of a chitosan-CNC (CS-CNCs) composite. CNCs were successfully isolated from waste paper by alkali treatment, bleaching, and sulfuric acid hydrolysis with FTIR and XRD analyses confirming successful extraction and a crystallinity index of 66.3%. TEM imaging revealed CNCs with a unique spherical morphology and diameters of 6–7 nm, significantly smaller than those reported in existing literature. Chitosan (CS), derived from shrimp shell waste, was integrated into the CNCs to form a composite thin film. This film, as revealed by SEM, had a homogeneous and consistent structure. The CS-CNCs composite demonstrated superior mechanical properties, with tensile strength increasing from 17.74 megapascal (MPa) in pure CS film to 22.08 MPa in composite, indicating its potential for robust and sustainable packaging materials. Soil degradation tests over 25 days showed a 24.7% degradation for CS-CNCs films, compared to 9.09% for CS films, underscoring their enhanced biodegradability. The composite exhibited notable antibacterial activity against Escherichia coli , suggesting its suitability for medical and hygiene applications. The measured contact angle of 80.4° indicates the film’s hydrophilicity, making it an excellent candidate for self-cleaning surfaces, such as textiles and windows. Remarkably, the CS-CNCs composite demonstrated exceptional photocatalytic degradation of Alizarin Red S dye, achieving 99.7% efficiency in 45 min, far surpassing the 87% efficiency of standalone CS films. The study showcases the green-synthesized CS-CNCs composite from waste paper offering an effective, eco-friendly, and economical approach for wastewater treatment due to its dual capabilities in dye degradation and antibacterial properties, while also opening avenues for its prospective application in self-cleaning surfaces, environmental remediation, and packaging thereby presenting a sustainable and economical solution for environmental cleanup and material innovation. Graphical Abstract

Different microscopy and scattering methods used in the literature to determine the dimensions of cellulose nanocrystals derived from cotton and bacterial cellulose were compared to investigate potential bias and discrepancies. Atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), depolarized dynamic light scattering (DDLS), and static light scattering (SLS) were compared. The lengths, widths, and heights of the particles and their respective distributions were determined by AFM. In agreement with previous work, the CNCs were found to have a ribbon-like shape, regardless of the source of cellulose or the surface functional groups. Tip broadening and agglomeration of the particles during deposition cause AFM-derived lateral dimensions to be systematically larger those obtained from SAXS measurements. The radius of gyration determined by SLS showed a good correlation with the dimensions obtained by AFM. The hydrodynamic lateral dimensions determined by DDLS were found to have the same magnitude as either the width or height obtained from the other techniques; however, the precision of DDLS was limited due to the mismatch between the cylindrical model and the actual shape of the CNCs, and to constraints in the fitting procedure. Therefore, the combination of AFM and SAXS, or microscopy and small-angle scattering, is recommended for the most accurate determination of CNC dimensions.

Cellulose nanocrystals (CNCs) derived from native cellulose can self-assemble into liquid crystals (LCs) and preserve the LC alignment in solid films that are attractive for the preparation of optical materials and devices from bottom-up manufacturing. Birefringent aligned CNC films provide the desired phase retardation for a narrow band of wavelengths due to the intrinsic wavelength-dependent birefringence of CNCs. Here, we produce a 1/4 λ achromatic CNC-based waveplate consisting of three layers of birefringent CNC films with phase retardations and slow axis directions, which are calculated by Jones Matrix, with optimized achromatic properties. Three uniform CNC films are prepared by aligning nematic CNC LCs doped with polyethylene glycol on patterned polydimethylsiloxane substrates. The fabricated achromatic waveplate is characterized by measuring the transmission spectra, and its maximum deviation of phase retardation is around 0.06 for the wavelength range of 460–660 nm. The achromatic performance is improved by one order of magnitude compared with the single birefringent CNC films. Our CNC-based achromatic waveplate has good optical homogeneity, flexibility and can be tailored into arbitrary shape.

In this work, three types of cellulose nanocrystals (CNCs) were used: CNCSO3H extracted from wood pulp by sulfuric acid (H2SO4), CNCCOOH extracted from cotton linters by ammonium persulfate (APS) and CNCCOOR obtained by esterification of the previous two CNCCOOH and CNCSO3H. For a comparative assessment of gas barrier performance, plastic films such as PLA, PET, PE, PP, OPP and OPA were selected, coated with the three types of CNCs and finally laminated with a solvent-based polyurethanic adhesive. First, all dispersed CNCs were characterized by apparent hydrodynamic diameter and Z potential by means of dynamic light scattering (DLS) and electrophoretic light scattering (ELS) techniques, respectively, followed by the crystallinity index (XRD), thermogravimetric analysis (TGA) and evaluation of Fourier-transform infrared spectroscopy (FTIR), as well as the charges density. The surface chemistry of coated plastics (CNCs-P) was assessed by the Z potential through the electrokinetic technique (streaming potential method) and the optical contact angle (OCA). Lastly, laminated films (P-CNC-P) were evaluated by gas permeability measurements at 23 °C and 50–80% RH. It is worth noting that improvements between 90% and 100% of oxygen barrier were achieved after the lamination. This paper provides insights on the choice of cellulosic nanomaterials for the design and development of advanced and sustainable food packaging materials.

Oil palm empty fruit bunch (EFB) biomass valorisation for high-value applications has been a current focus in research due to the vast amount of biomass generated from the daily operation of palm oil mills. EFBs can be utilized to produce high-value nanomaterials such as cellulose nanocrystals (CNCs), lignin-containing cellulose nanocrystals (LCNCs) and nanolignin (NL), as well as value-added products such as syngas, ammonia, methanol and electricity. More often, a single product processing pathway from EFBs entails a higher production cost relative to conventional petroleum feedstock. Therefore, the biorefinery concept is exploited to liberate the huge economic potentials of these products. However, different biorefinery schemes would have different environmental and economic performances. Thus, the evaluation of environmental and economic performances associated with various schemes of oil palm biorefineries is carried out in a two-step approach to provide future guidance in selecting suitable schemes for oil palm biorefineries. In the first step, a comparison of the environmental and economic performances of three different nanomaterial plants—CNC, LCNC and NL plants—was performed, and the results showed that the LCNC plant had the best environmental performance, while the NL plant had the highest profit margin. These nanomaterials serve as the core products for the development of biorefineries. In the second step, various nanomaterials, chemical products and power plants are integrated together to form a biorefinery. The scheme with LCNC and NL plants and power generation pathways via gasification yields the lowest environmental impact and highest profit margin. This analysis provides an early stage evaluation for future nanomaterial biorefineries from environmental and economic perspectives.Graphic abstract